.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/example_drifters.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_gallery_example_drifters.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_example_drifters.py:


Analysing a drifter dataset
============================

.. GENERATED FROM PYTHON SOURCE LINES 5-12

.. code-block:: Python

    import numpy as np
    import lzma
    import matplotlib.pyplot as plt
    import cartopy.crs as ccrs
    import xarray as xr
    import trajan as ta








.. GENERATED FROM PYTHON SOURCE LINES 13-14

Importing a dataset with two drifters in the Barents Sea

.. GENERATED FROM PYTHON SOURCE LINES 14-18

.. code-block:: Python

    with lzma.open('barents.nc.xz') as barents:
        ds = xr.open_dataset(barents)
        ds.load()





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:12 fv-az1024-670 h5py._conv[2149] DEBUG Creating converter from 3 to 5




.. GENERATED FROM PYTHON SOURCE LINES 19-21

This follows the CF convention for trajectories
https://cfconventions.org/Data/cf-conventions/cf-conventions-1.10/cf-conventions.html#_multidimensional_array_representation_of_trajectories

.. GENERATED FROM PYTHON SOURCE LINES 21-23

.. code-block:: Python

    print(ds)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    <xarray.Dataset> Size: 110kB
    Dimensions:        (trajectory: 2, obs: 2287)
    Dimensions without coordinates: trajectory, obs
    Data variables:
        lon            (trajectory, obs) float64 37kB 29.85 29.83 ... 21.14 21.15
        lat            (trajectory, obs) float64 37kB 77.3 77.31 ... 74.58 74.58
        time           (trajectory, obs) datetime64[ns] 37kB 2022-10-07T00:00:38 ...
        drifter_names  (trajectory) <U16 128B 'UIB-2022-TILL-01' 'UIB-2022-TILL-02'
    Attributes: (12/13)
        Conventions:          CF-1.10
        featureType:          trajectory
        geospatial_lat_min:   74.5454462
        geospatial_lat_max:   77.4774768
        geospatial_lon_min:   17.2058074
        geospatial_lon_max:   29.8523485
        ...                   ...
        time_coverage_end:    2022-11-23T13:30:28
        creator_email:        gauteh@met.no, knutfd@met.no
        creator_name:         Gaute Hope and Knut Frode Dagestad
        creator_url:          https://github.com/OpenDrift/opendrift
        summary:              Two drifters in the Barents Sea. One stranded at Ho...
        title:                Barents Sea drifters




.. GENERATED FROM PYTHON SOURCE LINES 24-25

A basic plot can be made very simply with Trajan

.. GENERATED FROM PYTHON SOURCE LINES 25-28

.. code-block:: Python

    ds.traj.plot()
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_001.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_001.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:12 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:12 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:12 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    2024-10-31 20:50:12 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:12 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:12 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:12 fv-az1024-670 trajan.plot[2149] DEBUG Creating new figure and axes..
    2024-10-31 20:50:12 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:12 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:12 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:12 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)




.. GENERATED FROM PYTHON SOURCE LINES 29-30

The figure can be customized, combining functionality from Trajan, Xarray and Matplotlib

.. GENERATED FROM PYTHON SOURCE LINES 30-37

.. code-block:: Python

    ds.isel(trajectory=1).traj.plot(color='b', label=ds.trajectory[1].values,
                                    land='mask', margin=3)
    ds.isel(trajectory=0).traj.plot(color='r', label=ds.trajectory[0].values)
    plt.legend()
    plt.title('Two drifters in the Barents Sea')
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_002.png
   :alt: Two drifters in the Barents Sea
   :srcset: /gallery/images/sphx_glr_example_drifters_002.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:13 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:13 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:13 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    2024-10-31 20:50:13 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:13 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:13 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:13 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:13 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    2024-10-31 20:50:13 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:13 fv-az1024-670 trajan.plot[2149] DEBUG Creating new figure and axes..
    2024-10-31 20:50:13 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:13 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:13 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:13 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:14 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.plot[2149] DEBUG Axes already exist on existing figure.
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)




.. GENERATED FROM PYTHON SOURCE LINES 38-39

Trajan includes methods to e.g. calculate the speed of the drifters

.. GENERATED FROM PYTHON SOURCE LINES 39-42

.. code-block:: Python

    speed = ds.traj.speed()
    print(f'Max speed {speed.max().values} m/s')





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    Max speed 1008.360274201437 m/s




.. GENERATED FROM PYTHON SOURCE LINES 43-46

We see that the max speed > 1000 m/s, which is a numerical error
due to some cases with GPS positions reported with very small time interval.
By removing all positions where time interval < 5 min, we avoid this problem.

.. GENERATED FROM PYTHON SOURCE LINES 46-50

.. code-block:: Python

    ds = ds.traj.drop_where(ds.traj.time_to_next() < np.timedelta64(5, 'm'))
    speed = ds.traj.speed()
    print(f'Max speed {speed.max().values} m/s')





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    Max speed 1.2873047098224348 m/s




.. GENERATED FROM PYTHON SOURCE LINES 51-53

Likewise, one can insert breaks (NaN) in the trajectories
whenever the time between points exceed a desired threshold, e.g. 3 hours

.. GENERATED FROM PYTHON SOURCE LINES 53-55

.. code-block:: Python

    ds = ds.traj.insert_nan_where(ds.traj.time_to_next()>np.timedelta64(3, 'h'))








.. GENERATED FROM PYTHON SOURCE LINES 56-57

Plotting trajectories colored by drifter speed

.. GENERATED FROM PYTHON SOURCE LINES 57-65

.. code-block:: Python

    mappable = ds.traj.plot(color=speed)

    cb = plt.gcf().colorbar(mappable,
              orientation='horizontal', pad=.05, aspect=30, shrink=.8, drawedges=False)
    cb.set_label('Speed  [m/s]')
    plt.title('Trajectories colored by drift speed')
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_003.png
   :alt: Trajectories colored by drift speed
   :srcset: /gallery/images/sphx_glr_example_drifters_003.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detecting time-dimension for "obs"..
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: obs, detected time-dim: time.
    2024-10-31 20:50:14 fv-az1024-670 trajan.accessor[2149] DEBUG Detected un-structured (2D) trajectory dataset
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:14 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.plot[2149] DEBUG Creating new figure and axes..
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:14 fv-az1024-670 trajan.plot[2149] DEBUG Plotting trajectory 0 of 2 with color
    2024-10-31 20:50:14 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)
    2024-10-31 20:50:15 fv-az1024-670 trajan.plot[2149] DEBUG Plotting trajectory 1 of 2 with color
    2024-10-31 20:50:15 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:15 fv-az1024-670 matplotlib.colorbar[2149] DEBUG locator: <matplotlib.ticker.AutoLocator object at 0x7f6de96d4690>




.. GENERATED FROM PYTHON SOURCE LINES 66-67

Histogram of drifter speeds.

.. GENERATED FROM PYTHON SOURCE LINES 67-73

.. code-block:: Python

    speed = ds.traj.speed()
    plt.hist(speed.values[~np.isnan(speed.values)], 100)
    plt.xlabel('Drifter speed  [m/s]')
    plt.ylabel('Number')
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_004.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_004.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 74-76

The peak at speed=0m/s is from the period where one of the drifters are on land (Hopen island).
This can be removed simply:

.. GENERATED FROM PYTHON SOURCE LINES 76-82

.. code-block:: Python

    speed = speed.where(speed>0.01)
    plt.hist(speed.values[~np.isnan(speed.values)], 100)
    plt.xlabel('Drifter speed  [m/s]')
    plt.ylabel('Number')
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_005.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_005.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 83-86

The positions of GPS based drifters are normally given at slightly irregular time intervals,
as drifters may be without GPS coverage for periods, and may get GPX fixes irregularly.
TrajAn contains the method `gridtime` to interpolate positions to a regular time intervel, e.g. hourly:

.. GENERATED FROM PYTHON SOURCE LINES 86-93

.. code-block:: Python

    dh = ds.traj.gridtime('1h')
    ds.traj.plot(color='r', label='raw data', land='mask')
    dh.traj.plot(color='b', label='hourly')
    plt.gca().set_extent([23.8, 25.0, 76.8, 77], crs=ccrs.PlateCarree())  # Zooming in to highliht differences
    plt.legend()
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_006.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_006.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:17 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.plot[2149] DEBUG Creating new figure and axes..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)
    2024-10-31 20:50:17 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: time, detected time-dim: time.
    2024-10-31 20:50:17 fv-az1024-670 trajan.accessor[2149] DEBUG Detected structured (1D) trajectory dataset
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:17 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.plot[2149] DEBUG Axes already exist on existing figure.
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:17 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)




.. GENERATED FROM PYTHON SOURCE LINES 94-96

Having the dataset on a regular time interval makes it simpler to compare with e.g. drift models,
and also makes some analyses simpler

.. GENERATED FROM PYTHON SOURCE LINES 96-102

.. code-block:: Python

    dh.isel(trajectory=0).traj.plot(color='r', label='Full trajectory')
    dh.isel(trajectory=0).sel(time=slice('2022-10-10', '2022-10-12')).traj.plot(
                color='k', linewidth=2, label='10-12 Oct 2022')
    plt.legend()
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_007.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_007.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: time, detected time-dim: time.
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected structured (1D) trajectory dataset
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:18 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: time, detected time-dim: time.
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected structured (1D) trajectory dataset
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.plot[2149] DEBUG Creating new figure and axes..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    /home/runner/micromamba/envs/trajan/lib/python3.11/site-packages/shapely/creation.py:119: RuntimeWarning: invalid value encountered in linestrings
      return lib.linestrings(coords, out=out, **kwargs)
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: time, detected time-dim: time.
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected structured (1D) trajectory dataset
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new plot object.
    2024-10-31 20:50:18 fv-az1024-670 trajan.plot[2149] DEBUG Plotting lines
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: time, detected time-dim: time.
    2024-10-31 20:50:18 fv-az1024-670 trajan.accessor[2149] DEBUG Detected structured (1D) trajectory dataset
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.plot[2149] DEBUG Axes already exist on existing figure.
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:18 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..




.. GENERATED FROM PYTHON SOURCE LINES 103-105

The original dataset had two dimensions `(trajectory, obs)` (see top of page), and time is a 2D variable.
For the gridded dataset (as with datasets imported from some trajectory models), dimensions are `(trajectory, time)` and time is a 1D Xarray dimension coordinate

.. GENERATED FROM PYTHON SOURCE LINES 105-107

.. code-block:: Python

    print(dh)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    <xarray.Dataset> Size: 46kB
    Dimensions:        (trajectory: 2, time: 1142)
    Coordinates:
      * time           (time) datetime64[ns] 9kB 2022-10-07 ... 2022-11-23T13:00:00
      * trajectory     (trajectory) int64 16B 0 1
    Data variables:
        lon            (trajectory, time) float64 18kB nan 29.82 29.77 ... 21.13 nan
        lat            (trajectory, time) float64 18kB nan 77.31 77.31 ... 74.58 nan
        drifter_names  (trajectory) <U16 128B 'UIB-2022-TILL-01' 'UIB-2022-TILL-02'
    Attributes: (12/13)
        Conventions:          CF-1.10
        featureType:          trajectory
        geospatial_lat_min:   74.5454462
        geospatial_lat_max:   77.4774768
        geospatial_lon_min:   17.2058074
        geospatial_lon_max:   29.8523485
        ...                   ...
        time_coverage_end:    2022-11-23T13:30:28
        creator_email:        gauteh@met.no, knutfd@met.no
        creator_name:         Gaute Hope and Knut Frode Dagestad
        creator_url:          https://github.com/OpenDrift/opendrift
        summary:              Two drifters in the Barents Sea. One stranded at Ho...
        title:                Barents Sea drifters




.. GENERATED FROM PYTHON SOURCE LINES 108-109

Plotting the velocity spectrum for one drifter

.. GENERATED FROM PYTHON SOURCE LINES 109-113

.. code-block:: Python

    dh.isel(trajectory=1).traj.velocity_spectrum().plot()
    plt.xlim([0, 30])
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_008.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_008.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:20 fv-az1024-670 trajan.accessor[2149] DEBUG Detected obs-dim: time, detected time-dim: time.
    2024-10-31 20:50:20 fv-az1024-670 trajan.accessor[2149] DEBUG Detected structured (1D) trajectory dataset
    /home/runner/work/trajan/trajan/trajan/traj.py:535: FutureWarning: The return type of `Dataset.dims` will be changed to return a set of dimension names in future, in order to be more consistent with `DataArray.dims`. To access a mapping from dimension names to lengths, please use `Dataset.sizes`.
      lenobs = self.ds.dims[self.obsdim]




.. GENERATED FROM PYTHON SOURCE LINES 114-115

Do a basic animation of the drift of the drifters

.. GENERATED FROM PYTHON SOURCE LINES 115-118

.. code-block:: Python

    ds.traj.animate()
    plt.show()




.. image-sg:: /gallery/images/sphx_glr_example_drifters_009.png
   :alt: example drifters
   :srcset: /gallery/images/sphx_glr_example_drifters_009.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2024-10-31 20:50:20 fv-az1024-670 trajan.traj[2149] DEBUG Setting up new animation object.
    2024-10-31 20:50:20 fv-az1024-670 trajan.animation[2149] DEBUG Animating trajectories..
    2024-10-31 20:50:20 fv-az1024-670 trajan.traj[2149] DEBUG No grid-mapping specified, checking if coordinates are lon/lat..
    2024-10-31 20:50:20 fv-az1024-670 trajan.plot[2149] DEBUG Creating new figure and axes..
    2024-10-31 20:50:20 fv-az1024-670 trajan.animation[2149] DEBUG Running animation.. frames: 1142





.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 8.697 seconds)


.. _sphx_glr_download_gallery_example_drifters.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: example_drifters.ipynb <example_drifters.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: example_drifters.py <example_drifters.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: example_drifters.zip <example_drifters.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_